单项选择题
A.碱B.酸C.偏碱D.偏酸
A.400一600hB.500一750hC.600一800hD.800一1200h
A.10%~20%B.30%~60%C.65%~70%D.80%~100%
A.130~140B.120~130C.110~120D.140~150
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